The Yellow Boxfish are hard to find on the dive sites around Koh Tao, I’ve seen them the most at White Rock dive site hiding in the stag horn coral with their little fins going. But they can be found around Asia, the Indian and Pacific oceans.
Ostracion cubicus can reach a maximum length of 45cm, the ones I have seen here have been no more than 10cm, bright yellow and cute.
Boxfish are also known for their armored and rigid (box) body which in most cases which makes it hard to move but it has evolved it’s style of swimming called ostraciiform locomotion. The body is made from armour plates with holes for eyes, mouth, tail and fins. When young it is bright yellow in color and as it grows and gets older the brightness fades and very old specimens will have blue-grey to black colouration with faded yellow. They are solitary fish accept at breeding time in spring when males hang round with up to 4 females. Their diet is mainly marine algae, worms, sponges, crustaceans, molluscs and small fish.
It looks small and cute but when injured or stressed it releases the neurotoxin tetrodoxin (TTX) from its skin that may prove lethal to the fish in the surrounding waters. The bright yellow color and black spots are a form of warning coloration to any potential predators. They can be very frustrating to divers and photographers as they go deeper into corals and holes when approached. If you are looking to take a photo approach slowly so as not to spook it, being careful of your bouyancy and equipment so you do not damage the marine environment or equipment.
You can find out more about learning to identify fish by studying the Fish Identification course online.